When it came to crime in the Wild West, train robberies were far more common than bank robberies. Banks had the problem of being within (literal) shooting distance of the sheriff's office. Not only was this not a concern with trains, but there was the added advantage of it often being uncertain in which jurisdiction the crime occurred. Colt Express applies an action programming mechanic to this scenario.
Gameplay consists of two phases; Scheming and Stealing. After everyone draws a hand of six Action cards, players will take turns either playing an Action card face up (adding a memory component to the game) or drawing three more cards, with the number of turns being indicated on the current Round card. Some turns may be marked as having a special effect, such as the player order being reversed or requiring that cards be played face down. Once Scheming is done, the cards are then resolved in the order they were played. Possible actions include moving to an adjacent car, switching to the roof or interior as appropriate, punching a rival bandit who is in the same location, firing at a rival bandit who is in an adjacent location, claiming a Loot token in your current location, or moving the Marshal to a car adjacent to his current location. Some Round cards will also have an event which occurs once the Stealing phase is over. The winning player is the one who has collected the most loot by the end of five rounds.
Both forms of initiating player conflict have their own advantages. Punching employs superhero physics, as it sends the targeted bandit flying into an adjacent car. In addition, he'll leave behind one Loot token of the attacking player's choice. Firing has more long term effects, where the attacking player adds one of his Bullet cards to the target player's deck. A Bullet card is unusable during the Scheming phase, effectively limiting the range of actions the player can take if he draws one. Another source of Bullet cards is the Marshal. Should the Marshal enter a car occupied by a bandit (or vice versa), the bandit's player adds one of the Neutral Bullet cards to his deck.
A common trope in Westerns is to have one or more characters walking on the roofs of the train cars while they're in motion. Colt Express employs some incentives to encourage this. While up top, the Move and Fire actions have a range of three. Since the Marshal never goes up top, it's also the best way to get around him (especially if you don't want him filling you with lead).
One of the more distinctive aspects of the game is how, instead of a board, the action takes place in a three dimensional cardboard model train. Assembling the cars is a snap thanks to the clear instructions provided. The different parts also fit together snugly, so there's no need to apply glue. The only potential issue is that thick-fingered gamers may have trouble handing Loot tokens and Bandit pawns inside the cars.
Since the conflict elements work better with at least three players, some modifications are necessary for a two player game. In this case, each player controls two bandits. To avoid the awkwardness of handing two sets of cards, players use combined decks consisting of one Marshal card and one of every other Action type for each of their bandits.
In conclusion, this is an excellent game for introducing gamers to the action programming mechanic. The playing of card face up makes it less likely for a player to get stuck with a useless action than what you get in many other action programming games. It also features one of the better two player fixes I've encountered.